Hydraulic power system



Sept 8, 1959 F. M. LITTELL Erm. 2,902,826

HYDRAULIC POWER SYSTEM Original Filed March 18, 1953 n 1 l l l l n .I

E M 5 m n m H L OW PRESSURE FLUID United States Patent @thee 2,902,826Patented Sept. 8, 1959 HYDRAULIC POWER SYSTEM Frederick M. Littell andChester M. Wig, Chicago, lll., assignors to F. J. Littell MachineCompany, Chicago, D1., a corporation of Illinois Original applicationMarch 18, 1953, Serial No. 343,206, now Patent No. 2,758,837, datedAugust 14, 1956. Divided and this application June 6, 1956, Serial No.589,743

3 Claims. (Cl. 60-53) The invention relates generally to hydraulic powersystems and has reference in particular to a simple hydraulic powercircuit including an electrically driven hydraulic pump and an hydraulicmotor and wherein flow of the hydraulic lluid in the circuit iscontrolled by relief valves and by a conventional control valve whichmay be solenoid actuated.

The hydraulic power system of the invention has been devised for use inthose installations where it is necessary to frequently start and stopthe driving motor. An electric motor is not entirely satisfactory insuch installations since excessive starting and stopping leads to rapiddeterioration not only of the electric contacts but of the motor itself.In the present hydraulic power system the electrically driven pump hascontinuous operation and intermittent operation of the hydraulic motoris secured by controlling the delivery of the high pressure fluid to thesame. In other Words, when the high pressure fluid is delivered to thehydraulic motor the same is operative, and the motor is renderedinoperative merely by diverting the high pressure fluid to thereservoir.

Therefore an object of the invention is to provide a new and novelhydraulic power circuit of simple design, which will be highly efficientin operation, and Vwherein controlled operation of the hydraulic motoris secured by controlling the delivery to said motor of the high and bya conventional control valve which may be n beyond the piston 36 withthe sump.

sures within the system will rise and fall as the Work load `applied tothe rotating shaft of the hydraulic motor may vary in magnitude.

Another object of the invention resides in the provision of an hydraulicpower circuit for producing operation of an hydraulic motor, the highpressure fluid inlet to the motor and the low pressure fluid outletthereof each incorporating a relief valve capable of adjustment forvarying the operating pressures as regards the inlet fluid entering thepump and the exhaust fluid leaving the pump.

With these and various other objects in view, the invention may consistof certain novel features of construction and operation, as will be morefully described and particularly pointed out in the specification,drawings and claims appended hereto.

In the drawings which illustrate an embodiment of the device and whereinlike reference characters are used to designate like parts:

Figure 1 is a schematic view illustrating the hydraulic system of theinvention and showing the solenoid actuy ated control valve in operativeposition; and

Figure 2 is a schematic view similar to Figure 1 but showing thehydraulic system with the solenoid actuated control valve in inoperativeposition.

Referring to the schematic disclosures of Figures 1 and 2, the reservoirfor the hydraulic power system is provided by a conventional container10 which is substantially filled with a fluid medium such as oil 11 toform the sump or reservoir for the hydraulic system, the top 12 of thecontainer being provided with the inlet opening 13 normally closed bythe threaded cap 14. The main power source for the hydraulic systemcomprises the electric motor 16 and by means of the legs 17 the saidmotor is suitably mounted on and securedV to the top wall 12 of thecontainer. The motor 16 drives the hydraulic pump 18 which is connectedby means of the conduit or piping 20 with the relief valve designated inits entirety by numeral 21. Relief valve 21 may be additionallydescribed as a by-pass valve. From said relief valve the conduit 22leads to the hydraulic motor 23 which is provided with the operatingshaft 24, the said shaft constituting the power take-off for thehydraulic power system of the invention. The conduit 2'5 leads from thehydraulic motor 23 and connects the same to a second relief valvegenerally designated by numeral 26. Relief valve 26 may be addi-`tionally described as a motor exhaust throttle valve. The Huid pump 18receives its supply of hydraulic fluid such as oil through tubing 27,which extends into the sump or reservoir within container 10 and has itsinlet end provided with the filter 28.

The uid from relief valve 21 is returned to the sump or reservoir undercertain conditions and accordingly said relief valve is provided withthe drain pipe 30 which extends through top wall 12 and terminateswithin the container. In a similar manner the relief valve 26 isprovided with a drain pipe or exhaust conduit 31 which also extendsthrough top Wall 12 to terminate with in the container. The hydraulicmotor 23 is provided with a bleed line 32 which is normally closed butwhich may be opened for draining the motor to the sump. The tubing 22 istapped as at 33 to provide a connection therewith for the supply line 34which leads to a cylinder 35 having the piston 36 and piston rod 37. Thepiston 36 is yieldingly biased in a direction toward the left by thecoil spring 38. A bleed line 40 may be provided for connecting thatportion of the cylinder 35 The ow of the hydraulic medium within thecircuit is controlled by means of a control valve Vor pilot valveindicated in its entirety by numeral 41 and which includes the solenoid42 operatively connected through stern 43 with the spool valve 44. Thecoil spring 45 lresiliently urges said spool valve 44 into an idling orinoperative position. Relief valve 21 is connected to the pilot `valve41 by the conduit 46 and a similar conduit 47 connects said pilot valvewith relief valve 26. A drain pipe 48 leads from the pilot valve to thesump and the passage 50 formed in the body of the pilot valve connectsthe conduit 46 with the said drain pipe. The valve members 51 and 52,which form part of the spool valve, operate Within the passage 53, andin one position of said members, such as shown in Figure l, the conduit46 is closed and conduitY 47 is connected through the passage 53 to thedrain pipe 48. In the other position of the valve members, such as shownin Figure 2, the conduit 47 is closed and conduit 46 is connectedthrough passage 50 to the drain pipe 48.

Referring more particularly to the relief valves, it will be seen thatvalve member 55 of relief valve 21 is adapted to engage the the valveseat 56, being resiliently 3 hydraulic medium such as oil through saiddrain pipe into the reservoir. The passage 58 provided in the flange ofthe valve member 55 is open at all times and thus the oilcan ow.thro-ugh the passage into chamber 60 above the ange portion of thevalve member, and said oil Will continue its llow through channel 61into the conduit 46. From said conduit 46 flow of the oil is controlledby the members 51 and 52 of the pilot valve. The valve member 55 isadditionally provided with a small passage 62 extending centrallythereof in a longitudinal direction from end to end of the member andthis passage 1n conjunction with the poppet valve 63 provides means forregulating the operating pressures within the hydrau-llc circuit forproducing actuation of the hydraulic motor 23. The poppet valve 63 isheld against its seat by coil spring 64 and thus the conduit 46 isclosed off by said poppet valve. The pressure exerted by the coil sprmg64 can be adjusted by hand wheel 65. When the hydraulic pressure withinconduit 46 is sufficient to cause release of the poppet valve 63, thehydraulic medium 1s permitted to flow through passage 62 in valve member55 and into drain pipe 30, being eventually delivered to the reservoir.Y

' The relief valve 26 is constructed similarly to relief valve 21, thesame including a valve member 67` adapted to contact valve seat 68,being resiliently urged in this direction by coil spring 70, whereby toclose off the drain pipe 31. The passage 71 in theflange portio-n of thevalve member permits the oil to ow into chamber 72 located above theVflange portion and said oil will continue its flow through passage 73which connects with the conduit 47. vThe end of said conduit 47 issimilarly closed by poppet valve 74 and which is held closed by coilspring 75. The pressure exerted by the coil spring can be adjusted byhand wheel 76 and the poppet valve 74l`thus functions in a manner toregulate the exhaust pressure from motor 23 of the oil owing through thecircuit.

Energization of the solenoid 42 of the pilot valve 41 moves the valvemembers S1 and 52 to the left against the tension of coil spring 45, asshown in Figure l, and the passage for the conduit 46 is closed tothereby prevent flow of the oil from conduit 46 through 50 to the drainpipe 48. As a result the pressures above and below the flange portion ofvalve member 55 are balanced and said valve member is caused to moveagainst its valve seat 56, thus closing off the drain 30. Accordingly,the oil instead of returning to the reservoir through the drain 30 isnow caused to flow through the conduit 22 to the hydraulic motor 23 andeventually the pressure of the oil will reach a value high enough tocause rotation of the operating shaft 24 and actuation of whatevermechanism is toY be driven by said shaft. The oil discharging from themotor 23 is delivered by the conduit 25 to the relief valveV 26. Sinceconduit 47 is open to the drain 48 thevalve member 67 of the reliefvalve 26 is unbalanced and is lifted olf of its seat 68 to open drainpipe 31. The oil exhausting from the motor 23 is thus discharged throughthe drain pipe to the reservoir.

As long as the solenoid 42 remains energized the hydraulic circuit willoperate to drive the motor 23. Upon deenergization of the solenoid thecoil spring 45 will function to return valve members 51 and 52 to theirinoperative positions, in which positions the conduit 46 is open throughpassage 5t? to drain 48, whereas, conduit 47 is now closed by valvemember 52. Since the hydraulic medium is now able to flow throughconduit 46, the valve member 55 will be unbalanced and the valve willlift from its seat 56 to cause opening of the drain 30. With the drainpipe open the hydraulic medium from the motor driven pump 18 isdelivered back toV the reservoir and the hydraulic motor 23 is notoperative so that the main operating shaft 24 thus remains idle. Thenonoperating position of the parts is disclosed in Figure 2.

In View of the foregoing, it Will be understood that the hydraulicpressures within the system will vary from a maximum during operation ofthe hydraulic motor 23 to a minimum when the said hydraulic motor is notoperative. Also the operating pressures may vary somewhat, depending onthe work load applied to operating shaft 24. For the maximum work loadapplied to shaft 24 the highest operating pressures will be required toeffect operation of the motor 23 and rotation of the A4said shaft. VAnyreduction-in Ythe work load will permit -a corresponding reduction inthe hydraulic medium within the system. Since the pressures ofthehydraulic medium within the circuit will vary, use can be made of thesevariable pressuresV to eiect control of associated mechanisni. For thispurpose the supply line 34 has connection with conduit 22 and the saidsupply line connects with the piston and cylinder combination 35, 36.When the pressures are a maximum the piston 36 will be forced in adirection towardthe right as .shownl in Figure l. Conversely, when the.pressures Vare, a minimum, the piston 36 will be actuated by coilspring 38 into aV position toward the left, as shown in Figure 2. Forexample, this` movement of thepiston as. affected by thevariablehydraulicrpressures within the circuit can be employed tovhydraulically apply and releaseY friction brake means formingpart ofmaterial feeding mechanismlsuch as may have utility in the feeding, ofmetal or other material in` continuous strip form to punch presses andthe like., For` a moreY complete disclosure of such automaticallycontrolled friction brake mechanism reference is made to the copendingapplication of Frederick M. Littell and Chester M. Wiig, Serial No.343,206, filed March 18, 1953 and entitled Hydraulically Powered Rackand Pinion Feeding Mechanism, now Patent No. 2,758,837 of which thisapplication is a division.

' What is claimedis: l

l. In a hydraulic power system, in combination, a container providing areservoir for a hydraulic medium, a hydrauliccircuit including a fluidpump and a fluid motor and conduit means connecting the said elements, abypass valve interposed in the 4conduit means between the motor and thepump and having a drain pipe leading to the reservoir, an exhaustthrottle valve having an exhaust conduit leading to the reservoir, otherconduit means connecting the exhaust outlet'of the motor with-thethrottle valve, a control valve providing valveV members havingoperative and inoperative positions, a drain pipe connecting the controlvalve with the reservoir, a lirst conduit connecting the control valvewith the by-pass Valve, a second conduit connecting thecontrol valvewith the exhaust throttle valve, the valve members of the control valvewhen operatively positioned closing a passage to the i'lrst conduit andopening a passage for connecting the second conduit with the drain pipeof they said control valve, said valve members when inoperativelyplositioned closing a passage to the secondv conduit and opening apassage for connecting the first conduit with. the drain pipe of thecontrol valve, the by-pass valveand the throttle valve eachhaving amember which is operative to close the inlet 'to the drain pipe of theby-pass valve and the inlet to the exhaust conduit of the throttle valverespectively, when the member is balanced by pressure of the hydraulicmedium within the valve, and said members being operative to open theinlet to the drain pipe and the inlet to the exhaust conduitrespectively, when the member is unbalanced by the pressure of thehydraulic medium, the Vsaid valve members of the control valve whenoperativelypositioned producing a balanced condition in the by-passvalveand an unbalanced condition in the throttle valve, andV wheninoperatively positioned producing. anvunbalanced condition in theby-pass valve and a balanced condition in the throttle Valve.

2. In a hydraulic power circuit, in combination, a container providing'a reservoir for a hydraulic medium, a hydraulic pump having an inletleading to the reservoir, a by-pass valve and an Aexhaust throttle valveeach havaan.

ing an interior valve chamber, a pipe connecting the outlet of the pumpwith the by-pass valve, conduit means connecting the respective chambersof the by-pass and throttle valves, a hydraulic motor interposed in theconduit means and located between the valves, said by-pass and throttlevalves each having a drain communicating the interior chamber thereofwith the reservoir, a memy ber within the chamber of each valve abovesaid drain and having operation to open and close the inlet to the draindepending on whether the member is balanced or unbalanced by thehydraulic pressures prevailing within the chamber of the valve, a ilowpassage provided in the by-pass valve and in the throttle valve andlocated above the member therein, each said member having an openingconnecting the passage above the same with the chamber below the member,and means for controlling the hydraulic pressures within the chambers ofthe valves, said means including a control valve also having a valvechamber therein, a drain pipe connecting the valve chamber of thecontrol valve with the reservoir, a iirst conduit joining the flowpassage of the by-pass valve with the valve chamber of the controlvalve, a second conduit joining the ow passage of the throttle valvewith the valve chamber of said control valve, and a valve memberoperating within the valve chamber of the control valve to control ow ofthe hydraulic medium from the irst and second conduits to the drain pipeofthe control valve.

3. In a hydraulic power circuit, in combination, a container providing areservoir for a hydraulic system, a hydraulic pump having the hydraulicmedium of the reservoir supplied to its inlet, a by-pass valve and athrottle valve each having an interior chamber, a pipe connecting theoutlet of the pump with lthe by-pass valve, conduit means connecting thevalves and providing a hydraulic circuit including said valves, the pipeand the pump, a hydraulic motor interposed in the conduit means andhaving its inlet connected to the by-pass valve and its exhaustconnected to the throttle valve, each Valve having a drain pipeconnecting the interior chamber thereof with the reservoir, a valvemember within the chamber of each said valve and having operation toclose and open the inlet to the drain pipe thereof depending on whetherthe valve member is balanced or unbalanced by the hydraulic pressuresprevailing within the chamber on the respective sides of the valvemember, means for controlling the hydraulic pressures prevailing withinthe chambers of the valves respectively, said means including a controlvalve and conduits connecting the said control valve with the by-passvalve and with the throttle valve respectively, on that side of thevalve member thereof opposite the drain pipe connection, and arelatively small passage formed in the valve member of the by-pass valveand also in the valve member of the throttle valve for connecting thechambers on respective sides of the members.

References Cited in the file of this patent UNITED STATES PATENTS1,615,341 Murray Jan. 25, 1927 2,275,321 Scates Mar. 3, 1942 2,451,013Ziskal et al. Oct. 12, 1948 2,479,359 Holt Aug. 16, 1949

